Dry placer mining apparatus



March 24,1942. L, MOLEAN v 2,277,497

DRY PLACER MINING APPARATUS Filed July .14, 19:?

Jy/e Mc 4am?v Patented Mar. 24, 1942 UNITED STATES PATENT OFFICE DRY PLACER MINING APPARATUS Lyle McLean, Los Angeles, Calif. Application July 1 4, 1937, Serial No. 153,562

1 Clainn (Cl. 209-474) My invention relates to dry placer mining apparatus.

The apparatus as shown and described herein is a connected unit yet the method of doing the work having the several stages of advantageous performance with the several novel details may be carried on under this invention without necessarily embodying the complete unit as herein shown. 1

Reference will be had to the accompanying drawing in which- Figure 1 is a side elevation, partly in section, of one of the recovery boxes or units, being the final stage of recovery of the concentrates and this particular unit is for the. recovery of the coarse mineral or nuggets.

Figure 2 is a section on line 2-2 of Fig. 1.

In the legs 4| there are provided slide gates 50 adapted to allow the operator to regulate the flow of material to the several boxes 42 to accommodate for the varying capacities of the boxes to dispose and separate the material delivered to them.

The construction of the concentrating boxes are indicated-by Figures 1 and 2. inclusive and operate on the principle of having an air fan 44 at each box which discharges a large volume of air into an equalizing chamber 53 and through a curved screen 49, on which screens are deposited the material from which the concentrates are separated from the lighter material by the air currents coming up from the fans. The removal from the curved screen 49is accomplished by access to the screen by lifting the hinged cover 55 of Fig. 1.

It is highly desirable that the means of pro ducing the air currents up the recovery boxes be located as closely as conveniently possible under the chambers 53 and thus fans for thispurpose are located directly under each box. Air streams of length allow a wider variation of lines of air currents on arriving at the points of service than short streams. Services of these concentrating boxes indicate better results obtained where fans are directly below the concentrating boxes as here shown.

The method of operation is to so regulate the air coming from the fan and passing through the screen and material thereon as to produce gentle bubbles of dust sand and that will rise out of the material leaving the heavier portions in which are the concentrates and the lighter materialbe carried over and down the ducts 4,3 to a carrier belt (not shown).

To aid in evenly distributing the air over the surface of the screens there are deflecting vanes 41 Fig. 2. The vanes 47 are arranged'in varying angles to the screen to distribute the air evenly under the screen as the air flows up from below.

It is desirable to have clean air and dry as may be had from a dry desert atmosphere to enter the fans for passing through the material and to this end the air supplied to the fans 44 is conducted to them by pipes 46 from a source as best available.

It is necessary to control the air supply rightly needed at each concentration box, to provide the best concentration for the special grade of material to be treated at a particular box.

Below the coarse screen 32 the final and coarse concentration takes place at the box having the curved or bagged screen as shown in Figure 1. The coarse material handled at this box requires a strong air current and in order not to remove values of coarse concentrates the deep baggy bottom of the screen of Fig. 1 requires the air to lift the lighter waste material over the projecting wall 5| leaving heavy nuggets and concentrates on the screen.

The air that is driven through the boxes 42 also acts as drying agent for the material treated on these screens.

A modification which is illustrated in Figures 11 and 12 discloses a plurality of screens of progressively increasing mesh and means for reciprocating the same forming an alternative screen ing to on end and a discharge opening from the other end, a screen supported in the box between said admission and discharge openings arranged to provide a depressed separation chamber, the floor of which, in longitudinal vertical section, is of a downwardly convex curvilinear contour, and a source of air under pressure and communication therefrom to the underside of said screen for supplying a column of air through the separation chamber to the screen and upwardly through the separation chamber to gravitationally stratify the material for separating the gold-free refuse from the values, the curvilinear form of said chamber floor acting to impart a swirling action to the air forced through the interstices of the screen.

LYLE MCLEAN. 

